An amount at compound interest sums to Rs.17640/- in 2 years and to Rs.18522/- in 3 years at the same rate of interest. Find the rate percentage

The difference of two successive amounts must be the simple interest in 1 year on

the lower amount of money. 

S.I = 18522/- - 17640/- = Rs. 882/- 

Rate of interest = (882/17640) × (100/1) => 8820/1764 = 5% 

Principal = Amount/(1 + R/100)n 

= 17640/(1 + 5/100)2 

= 17640/(21/20 × 21/20) 

= 17640/(1.05 × 1.05) 

= 17640/1.1025 

= 16000

Thus the principal is Rs.16000/- and the rate of interest is 5%